Electrical musical instruments



' y' 1956 5.1. KRAUSS L 2,755,695

ELECTRICAL MUSICAL INSTRUMENTS Filed 001;. 25, 1950 BASS 7 TREBLE TREBLE BASS e mus 6525255 Jfeams United States Patent ELECTRICAL MUSICAL INSTRUMENTS Serge L. Krauss and Charles J. Tennes, Elkhart, Ind.,

assignors to C. G. Conn Ltd., Elkhart, Ind., 21 corporation of Indiana Application October 25, 1950, Serial No. 192,094

4 Claims. (Cl. 841.2)

This invention relates to electrical musical instruments and more particularly to electronic instruments of the organ type.

Electrical instruments of several different types have been proposed in which electric currents are generated and are mixed and controlled and used to drive a loudspeaker. Such instruments necessarily involve complications in the generation and control of the currents to produce the desired flexibility of operation.

It is a primary object of the present invention to provide an electrical musical instrument which involves a minimum number of parts and yet provides extremely great flexibility and versatility in operation.

Another object is to provide an electrical musical instrument in which tone currents falling in different selected frequency ranges can be variably attenuated in the output circuit. This not only enables the tonal quality to be controlled but also enables a desired balance or taper to be achieved with a minimum of complications.

Still another object is to provide an electrical musical instrument in which tone currents of different character are individually controlled and are mixed in selected intensities to produce different tonal eifects. According to one feature certain of the tone currents may be filtered or attenuated to change their wave form, thereby further to increase the tonal resources of the instrument.

The above and other objects and advantages of the invention will be more readily apparent from the following description when read in connection with the accompanying drawing, in which:

Figure l is a partial circuit diagram of an electrical musical instrument embodying the invention;

Figures 2 and 3 are partial simplified diagrams illustrating modified forms of base and treble controls; and

Figure 4 is a partial simplified diagram showing different forms of tone control circuits.

In the instrument as shown in Figure 1, the tone currents are generated by oscillators of a type more particularly shown and described in our co-pending application Serial No. 188,990. It will be understood that there is a separate oscillator for each note desired, so that a complete instrument may embody 85 or more oscillators. Each oscillator as illustrated, comprises a triode vacuum tube whose plate is connected through a series resistor 11 and keying switch 12 to a +B source indicated at 13. The plate may also be connected to ground through a condenser 14 which cooperates with the resistor 11 to control the attack and release characteristics of the instrument. The cathodes are connected through coil 24 and through a resistor 17 to ground, thereby to complete a circuit with the tube plates. The cathodes of the several tubes are connected through the resistor 17 to ground in parallel, and each of the oscillators has its own mixer resistor, as indicated at 18, 18' and 18", etc. Preferably the oscillators are divided into banks of an octave or more, as desired, with the mixer resistors 18, 18 etc., connected to ground through a common condenser 19.

Pulse currents are developed in this circuit and are maximum flute tone is provided. By opening and closderived therefrom by means of a transformer having a primary winding 21 connected across the resistor 17 and a secondary output winding 22.

Each of the oscillators also develops a sine wave current which is derived from a connection 23 between the mixer resistors 18'and the condensers 19, as shown. The cathodes of the tubes are connected to taps on coils 24 shunted by condensers 25 and forming tank circuits for the oscillators. The tank circuits are connected through grid condensers 26 to the control grids of the tubes, which are also connected through resistors 27 to a point between resistor 15 and condenser 16, as shown. The resistor 15 is connected to the +B source and through the condenser 16 to the high side of resistor 17.

The several oscillators or groups of oscillators are preferably divided into banks, and the connections 23 of each group of banks may be connected through resistors 28 to flute buses 29. The flute tones from the several buses are mixed in a mixer unit and supplied simultaneously therefrom to the output circuit. As shown, two buses are contemplated and the currents therefrom are mixed by a mixer, including a pair of triode tubes 31 whose plates are connected to a +B supply through load resistors 32, and are interconnected through series resistors 33. The cathodes of the tubes 31 are grounded through a cathode resistor 34 and the grids thereof are connected to the flute bus bars through connections, one of which is shown at 35. The mixed flute tones are taken off from a point between the two resistors 33 through a condenser 36 and resistor 37.

Tremolo currents may be supplied to the generators from a tremolo generator 38 connected through a transformer 39 to a plurality of series connected resistors 41. A tap connected from the +13 source to the primary of the transformer 39 supplies power to the tremolo generator. The grids of the first set or bank of oscillators may be connected directly to the lower end of the secondary of transformer 39 through their grid resistors 27, as shown. Succeeding banks of oscillators may have their grids connected to points between the successive resistors 41 so that different amounts of tremolo voltage will be supplied to the different banks of oscillators. In this way the amount of tremolo or the tremolo balance throughout the entire keyboard is controlled as desired. The top end of the series resistors 41 is returned to ground, as illustrated generally by the dotted connection 40, to provide the necessary return from the grids of the oscillator tubes 10 to their respective cathodes.

For the output of the instrument the pulse and sine Wave or flute tones are mixed and are supplied through an amplifier 42 to a loudspeaker 43. The amplifier is preferably connected to the output circuit of the instrument through a potentiometer 44 controlled by an expression pedal to regulate the overall amplitude of the instrument. The output circuit is supplied from a mixer, including a pair of tubes 45 whose cathodes are grounded through a resistor 46 and whose plates are connected to a +13 source through plate resistors 47. The plates of the tubes are interconnected by resistors 48, and the output circuit is connected to a point between the resistors 48 through a blocking condenser 49.

The flute signals from the flute mixer are supplied to the grid of one of the tubes 45. To control the amount of flute tone in the output a control circuit is inserted in the connection and, as shown, comprises three resistors 51 connected in series from the flute mixer output to ground with switches 52, by means of which all or any portion of the resistors 51 can be selected. In the position shown the flute tone will be cut off or at minimum volume. When the right hand switch is thrown to the right the resistors 51 are all in the circuit so that Masses ing the switches 52, more or less of the resistors can be cut in to control the flute tone volume as desired.

I The pulse tonedeveloped in the transformer winding 22 is. utilized to produce both a string and a reed e ect For the string effect the pulse tone is used substant ally as generated, and its volume is controlled bya unit similarto that described above for the flute tone control, shown, the unit comprises a plurality of series resistors 53 connected between a center tap on the winding 22 and :ground anda series of switches 54 by means of which the resistors 3 can be cut into or out of the circuit. I The string tone control circuit as shown is connectedthrough a blocking resistor 55 to the grid of the he m x n u 5- 'Io develop reed tones the pulses are filtered in a resonant ;circuit which includes an inductance coil 56 connected. across the transformer winding 22 through abloeking resistor- 57. More or less capacitanee can be connected in parallel with the coil 56, and as vshown for this-purpose a plurality of eondensers 58 .are connected between one end of the coil 56 and, ground through control switches 59. By opening and closing the switches 59 in proper sequence the tuning of the circuit can be varied to alter the wave form of the pulsesdifferently andto control the volume of reed tone supplied toithe V t I I The mixed pulse and flute tones provided by themixi g tubesfiS are supplied through the output circuit to the amplifier. 'In order to controlthe taper of themstrurnent as well as to provide greater tonal contrast bass and treble control circuits are provided in the output circuit. As shown in Figures 1 and 2, the bass control comprises a condenser 61 in series in the output circuit, which is shunted by a variable resistance indicated at 62 in Figure 2. "shown in Figure 1, the variable resistance 62 may be provided by series resistors 62, which are selectively cut into and out of the circuit by switches 63;; In this construction the condenser 61 offers less resistance to the high frequency tones than to the low frequency tones, so that the low frequency tones are attenuated to ag'reater extent than the high frequency tones by -'the resisto'r 62. Y I

In the form shown in Figures land 2 the treble tones are controlled by a capacitor 64 connected in shunt across the-output circuit. As illustrated in Figure 1, this variable eapacitor V may comprise a pair of condenser's 64 connected between the hot side of the output circuit and ground and cut into or out of the circuit by switches 65. By adjustment of the amount of capacity in shunt across the output circuit the high frequency tones may be bypassed to the desired extent without materilly affecting the lower frequency or bass tones.

Figiire 3 illustrates analternative bass and treble cont-rol "arrangeme t in which the tone generating source is indicated generally at 66 as supplying an output 'p'otentidme'ter A l' Thesource 66 is connected through resisters 67, which may represent the internal resistance of the'tubes and the circuit components to the potentiometer. To control the bass tones a variable inductance 68 isconnected 'in shunt across the circuit variably to bypass the lower frequency currents without materially affectthe higher frequency currents. The high frequency or treble tones are controlled by a variable inductance 69 in series in the line which will 'e xert a variable chdcking effect ion the high frequency currents without materially affecting the low frequency or bass notes. v

It will be u'nderstood tha't in the complete instruirient the ususl keyboa'rd inyolying one, two, or more manuals W apedal board may be provided connectcdio Control the difiere'nt osc llators through the usual coupling circuits I'hese .coupling citcuits, together with the. tone cgrttro l providcd to vary the intensities of the flute string tones and the-reed control circuit tol pjroylide dif- QIQQ .99PiY ..I d ces s re 'Q th tins utn nt extremely large flexibility and enormous tonal resources.

Further, tonal effects can be achieved through the base and treble controls which will modify selectively the strengths of the different tempered harmonics without requiring the complications which would be necessary to change the amplitudes of the tone frequency generators. This control additionally enables the organist to accentuate a particular section of the manual as for example, to bring out a solo melody while other portions of th ame m n lvor he o er man ls may e, te uated for accompaniment. withoutsproducin'g an abrupt-point of change at some point in the keyboard. Through the use ofthese several controls an almost unlimited number of different musical effects and combinations are 'possible, so that a. relatively simpleiiistrument becomes capable of the flexibility of operation ordinarily possible only with relatively complicated and expensive instrue s!" K r rf'? Additional pleasingeff'ects can bepr odueedandfurther versatility can be provided in the instrument throng the use of resonant controls in theoutput circuit as indie ted in F ig'ure 4, As shown parallelresonant ct; is proyided including an inductai fi fi oil 71 havinga variable condenser 72 n paralleltherewith across the output cit; cuit. I hi s will pass the signals at the resonant frequency and will attenuate signals both above and below the resonant frequency. Additionally a series resonant cirbri ifclnding senescenc coiljfi with a variable condenser 74 in series therewith is connected across the autism circuit. This circuit will provide greatest attenuation for signals at its resonant frequencyandlessattenuation of signals'abeve and below resonance. The resonant circuits may be made effective or ineffective as desire'dfby switches. 75. It will be understood that these resonant circuits can beruse'd in addition to the bass and treble controleircuits described above. p 2 l The several controls in the output circuit enable a wide varietylof interesting and'useful musical effects to be obtained, For exa'mple, using only the flute tones and setting the couplers to borrow desired harmonics, it i's possible by selecting the desired controls and adjusting them properly toduplicate most of the effects obtainable through tone synthesis without the complications involved in. adjusting the amplitude of particular partials at the generators. By using mixtures of the flute and pulse tonesfand the output controls a'n al most endlcssvartety of effects can be produced sincethe cp'rato'r has full controlof theha rmonic structure of the tones. While the invention has been shown. and desc jtbedvin connection with one particular type of g tone generators and with specifictone control circuits, it will be u derst ood that this Jshbwirigis illustrati e only and is not to be taken as a definition of the scope. ofthe inventionreference eing had for this purpose to the appended claims.

isjclaiined is: I t electrical musical .instrument cemprisin 'a'p ity of generators each including a finst'irieans to generate a sine wave current and a second means to generate a current richfinharmonics a mixing device, afir ircuit connectingthefirst means to the device, an adjustable attenuating device in the first .circuit variablyto attenuate the sine wave currents, asecond circuit connecting the secondimeans to the mixing device, an adjustable attenuatinggdeviee in the secondfcir'cuit variably to attenuate the currents rich in harmonics, a third circuit'c nectirig the secon d means to the niixi i dvioe, and elements the third circuit atleast oneof which aga ns able, formi ng a resonant circuit to change the waveform of the currents rich :in h armonics. An electrical m'usical instrumentcomprising 1- ity of generator s each including a first means to "gene t e a sine wave current and a second means tofgerieratefa current :rich in harrrionics, a mana es/ ce, a firfstcircuit connecting the nrstmeans"to the mixingdeyice, an a ustable attenuatingdevice in the fl r st circuit ly to attenuate the sine wave currents, at second circuit connecting the second means to the mixing device, an adjustable attenuating device in the second circuit variably to attenuate the currents rich in harmonics, a third circuit connecting the second means to the mixing device, elements in the third circuit at least one of which is adjustable, forming a resonant circuit to change the wave form of the current rich in harmonics, an output circuit connected to the mixing device, and adjustable attenuating devices in the output circuit selectively to attenuate currents having frequencies falling in a selected range.

3. An electrical musical instrument including in combination, generator means for generating sine wave currents of different audible fundamental frequencies and currents of different audible frequencies which are rich in harmonics, a mixing device, circuit means connecting said generator means to said mixing device and including a first circuit portion for applying said sine Wave currents to said mixing device and a second circuit portion for applying said currents rich in harmonics to said mixing device, said first circuit portion including adjustable attenuating means, said second circuit portion including adjustable attenuating means and adjustable resonant means for selectively changing the wave form of the currents rich in harmonics, and an output circuit connected to said mixing device including adjustable impedance means selectively effective only for currents below a predetermined fundamental frequency in the audio range variably to attenuate the relatively low frequency currents in said output circuit corresponding to the bass notes, said output circuit including second adjustable impedance means selectively effective for currents above a predetermined fundamental frequency in the audio range variably to attenuate the relatively high frequency currents in said output circuit corresponding to the treble notes.

4. An electrical musical instrument comprising a plurality of tone generators to generate currents of different fundamental audio frequencies, at least a part of said generators having a first output providing sine Wave cur rent and a second output providing current rich in harmonics, mixing means, circuit means selectively applying currents from said outputs of said generators to said mixing means, said circuit means including a first circuit portion connected to sad first outputs of said generators and a second circuit portion connected to said second Outputs thereof, said first circuit portion including adjustable attenuating means for attenuating said sine wave currents, said second circuit means including adjustable attenuating means and adjustable resonant means for changing the Wave form of said currents rich in harmonics, an output circuit for said mixing means, a pair of adjustable filtering means connected to said output circuit and effective respectively only on tone currents having fundamental frequencies above and below predetermined values in the audible range variably to attenuate the high and low frequency currents respectively, and adjustable resonant filter means tuned to a frequency substantially the same as one of said fundamental audio frequencies selectively connected to said output circuit variably to attenuate currents whose frequencies fall in a selected range.

References Cited in the tile of this patent UNITED STATES PATENTS 1,984,450 Aceves Dec. 18, 1934 2,251,051 Hammond July 29, 1941 2,328,282 Kock Aug. 31, 1943 2,332,076 Hammond et a1 Oct. 19, 1943 2,340,001 McKellip Jan. 25, 1944 2,340,002 McKellip et al. Jan. 25, 1944 2,403,664 Langer July 9, 1946 2,485,751 Larsen Oct. 25, 1949 

